Dual-conjugate adaptive optics for wide-field high-resolution retinal imaging

Department of Ophthalmology, University of Gothenburg, Sweden.
Optics Express (Impact Factor: 3.49). 03/2009; 17(6):4454-67. DOI: 10.1364/OE.17.004454
Source: PubMed


We present analysis and preliminary laboratory testing of a real-time dual-conjugate adaptive optics (DCAO) instrument for ophthalmology that will enable wide-field high resolution imaging of the retina in vivo. The setup comprises five retinal guide stars (GS) and two deformable mirrors (DM), one conjugate to the pupil and one conjugate to a plane close to the retina. The DCAO instrument has a closed-loop wavefront sensing wavelength of 834 nm and an imaging wavelength of 575 nm. It incorporates an array of collimator lenses to spatially filter the light from all guide stars using one adjustable iris, and images the Hartmann patterns of multiple reference sources on a single detector. Zemax simulations were performed at 834 nm and 575 nm with the Navarro 99 and the Liou- Brennan eye models. Two correction alternatives were evaluated; conventional single conjugate AO (SCAO, using one GS and a pupil DM) and DCAO (using multiple GS and two DM). Zemax simulations at 575 nm based on the Navarro 99 eye model show that the diameter of the corrected field of view for diffraction-limited imaging (Strehl >or= 0.8) increases from 1.5 deg with SCAO to 6.5 deg using DCAO. The increase for the less stringent condition of a wavefront error of 1 rad or less (Strehl >or= 0.37) is from 3 deg with SCAO to approximately 7.4 deg using DCAO. Corresponding results for the Liou-Brennan eye model are 3.1 deg (SCAO) and 8.2 deg (DCAO) for Strehl >or= 0.8, and 4.8 deg (SCAO) and 9.6 deg (DCAO) for Strehl >or= 0.37. Potential gain in corrected field of view with DCAO is confirmed both by laboratory experiments on a model eye and by preliminary in vivo imaging of a human eye.

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    • "A few reports have discussed various benefits of MCAO in the context of microscopy [9] [10], though these have relied on numerical simulation only. MCAO has also been used in retinal imaging applications [11] and in benchtop experiments designed to simulate astronomical imaging [12]. Our goal here is to build on these results by providing a theoretical framework specifically tailored to the microscopy community. "
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    • "A dedicated optical system with components producing variable amounts of astigmatism and field curvature could help to eliminate the lower-order ocular aberrations over a larger central field. Using a variable low-order field aberration corrector in conjunction with an adaptive optics system might be an alternative to the multi-conjugated AO system proposed recently [61, 62]. Assuming such a system is well corrected for the lower-order field-dependent aberrations (field curvature and field-dependent astigmatism) one may imagine the possibility of incorporating static elements in the pupil conjugate plane which correct typical values of spherical aberration c(4,0), which is field-independent. "
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